You are very limited regards the swingarm/wheel combo. Nearly everything needs modding, to varying degrees, to fit in the narrow Lc frame, which is approx. 200mm across the pivot. Lots of guys use Rgv arms, but they are longer by approx. 4";
They are a "marmite" swingarm for most - some don't mind the extended look of the bike, others are not so keen ! It will change the handling characteristics of the bike, and the mod for the shock can be an expensive thing to get done. A lot of the more modern swingarms don't have any top loops like the Lc needs, as the Ypvs style upright shock became more popular through bikes like the Tzr/Kr1/s/Rgv etc, and the more modern, bigger bikes often need the frame widened to get a swingarm in and chain run anywhere near. I'm pretty sure a Tzr250 rear wheel will go into an Lc swingarm with a couple of simple spacers - I think Rich on here has done that, and Jon too ? Metmachex will make you a lovely box section swingarm to the correct dimensions for the Lc, with slotted chain adjusters, chain slider etc for about £500 brand new, which I think is a hard price to beat when you consider what you may end up spending on a second hand arm that needs modding/painting/polishing/new bearings etc. Front ends are much easier normally !! Just my opinion
If You are are a bit patient check all the TZ or racer websites and for sale sites. You can find Ally swing arms from TZ's which will need minor modification and is the same or very close to the standard wheel base of an LC.
As you can see the wheel base is the same, but it does look a bit plain Jane. The construction around the two pivot points for the chassis and the shock is very strong. Similar to the Metmachex TZ arm
the yz 250 arm is a touch shorter than the 465 arm. I had a 465 one in an 250LC frame until some fud stole the bike, i got it back but the arm was last seen in a scrappies..on the plus side, the capacity had risen by 100 cc.. The mount on the frame was moved a bit further forwards and an rd125 shock was used as well to get the ride height back. I bought a 250 and a 465 arm from a MX breaker years ago to replace the stolen one but need a rd shock to sort it all out.. the mx swingarm is a bit narrower so i had spacers made up but haven't got any more done.. bike is about 150 miles from where i live so ain't too high on the priority project list.. oh and there was a notch cut out of the arm to allow the chain to run freely. unlike the LC swingarm there was no flex in the alloy yz one